Thimerosal (“Mercury”) in Vaccines

As you may know, one of the “loudest” controversies surrounding vaccines is whether they trigger (specifically, if thimerosal triggers) autism. After having reviewed three books on vaccines in general, with one focused on autism in particular, I can now better understand why there is so much confusion. The first two books — The Vaccine Book (2007) and What Your Doctor May Not Tell You About Children’s Vaccinations (2001), both of which are written by M.D.s — got me very upset about vaccines and mercury, in particular. For example, reading the following was quite upsetting as a parent:

Between 1991 and 1999 the United States embarked on what might be labeled a bold, ill-planned experiment: the recommended vaccination of newborns with the hepatitis B vaccine. This vaccine contained 12.5 micrograms of mercury (thimerosal), which is more than twenty-five times the EPA “safe level” of 0.1 microgram per kilogram of body weight per day. This toxic dose was followed by not one but two more doses: one at one to two months and another at six months of age. In addition, infants and children were also given four doses of mercury-containing Hib at two, four, six, and twelve to fifteen months of age; plus four doses of mercury-containing DTP at two, four, six and twelve to eighteen months of age. By the age of six months, vaccinated children had received 187.5 mcg of mercury — a poison that accumulated in their bodies because production of bile, which helps clear toxins from the body, is not developed in children less than four to six months of age.

When mercury can’t get out of the body, it travels to the brain, changes into inorganic mercury, clings to brain tissue, and damages the nervous system. Mercury doesn’t cling to just any part of the brain; it goes exactly to those areas involved in autism: the cerebellum, amygdala, and hippocampus.

However, Autism’s FalseProphets (2008) by Paul Offit, M.D. was able to incorporate the most updated studies on the thimerosal – autism controversy and it did a good job of detailing why the thimerosal journey has been so confusing. The fact is: it wasn’t until 2008 that researchers had more relevant information.

In 2001, vaccines were removed from childhood vaccines, except for some flu vaccines. Since autism is generally diagnosed when children are between three and five years of age, six years should be sufficient time by which to assess whether rates of autism would decrease from the absence of thimerosal. During this thimerosal-free period, it was reported that autism rates were decreasing, which led parents to believe that thimerosal did trigger autism in some children. By the end of six years without thimerosal, however, rates of autism had increased. Below are notes from my readings.

Thimerosal’s Role in Vaccines

Thimerosal, a preservative containing ethyl mercury that has been in vaccines since the 1930s, is used to prevent inadvertent bacterial and fungal contamination of multi-dose vials. H1N1 vaccine distributed in multi-dose vials will contain about 25 micrograms of ethyl mercury per dose. The issue of thimerosal received public attention in 1999 when the American Academy of Pediatrics and the United States Public Health Service took the precautionary step of asking that thimerosal be removed from single-dose vials of all vaccines. This was done in such a precipitous and frightening manner that it gave rise to the notion that thimerosal had led to autism or mercury poisoning. It hadn’t.

In fact, subsequent studies found that infants could safely receive eight times as much mercury as is contained in the H1N1 vaccine. But the public’s perception of thimerosal was damaged. This year, enough thimerosal-free vaccine is available to inoculate children under age 6, but that does not mean doses with thimerosal are unsafe.

Thimerosal, a mercury-based preservative, was removed from childhood vaccines in 2001. It is still present in some influenza vaccines. Thimerosal is still used in the manufacture of some vaccines to prevent contamination. The thimerosal is removed at the end of the manufacturing process. In some cases, a tiny amount of thimerosal remains. The remaining amount is so small, that it is not possible for it to have any effect. Valid scientific studies have shown there is no link between thimerosal and autism. In fact, autism rates have actually increased since thimerosal was removed from childhood vaccines. The American Academy of Pediatrics (AAP), the American Medical Association (AMA), the CDC, and the Institute of Medicine (IOM) agree that science does not support a link between thimerosal in vaccines and autism.

“In January 2008 — six years after thimerosal had been removed from vaccines given to young infants in the United States — health officials from California announced the state’s most recent rates of autism. Because children with autism were typically diagnosed between three and five years of age, six years of thimerosal-free vaccines should have been enough time to see whether the rates of autism had decreased. They hadn’t. The short-lived trend downward in 2004 had been falsely interpreted. In fact, the rates were increasing — dramatically. The grand experiment had been performed, and the results were clear. Robert Davis, then head of the Immunization Safety office at the CDC, stated the obvious: “If you remove cars from the highways, you’ll see a marked decrease in auto-related deaths. If thimerosal was a strong driver of autism rates and you remove it from vaccines, [researchers] would have seen some sort of decline — and they didn’t.”

“In August 2003, Paul Stehr-Green published a paper in the American Journal of Preventive Medicine. Stehr-Green studied children with autism in Sweden and Denmark from the mid-1980s through the late 1990s. He found the risk of autism increased after thimerosal had been removed from vaccines. By the late 1990s, when health officials had completely eliminated thimerosal, the number of children with autism was higher than it had ever been, exactly the opposite of what would have been expected if thimerosal caused autism…

In September 2003, Kreesten Madsen, an epidemiologist from the University of Aarhus in Denmark, published a paper in Pediatrics. Madsen examined the medical records of 1,000 children diagnosed with autism between 1971 and 2000. Like Stehr-Green, he found that between 1992 and 2000, after thimerosal had been removed from vaccines in Denmark, the incidence of autism skyrocketed. Madsen concluded the data “did not support a correlation between thimerosal-containing vaccines and the incidence of autism.”

In October 2003, Anders Hviid, an investigator from the Danish Epidemiology Science Center in Copenhagen, published a paper in the Journal of the American Medical Association. Hviid studied the records of Danish children between 1990 and 1996, during which time thimerosal had been removed from vaccines. Like Madsen and Stehr – Green, Hviid found the number of children with autism increased after thimerosal had been eliminated. He concluded, “The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic spectrum disorder.”

One year later, in September 2004, Jon Heron, an epidemiologist from the University of Bristol in the United Kingdom, published a study in Pediatrics. Heron examined the records of 14,000 children who had received different amounts of thimerosal in vaccines between 1991 and 1992… The more thimerosal children received, the less likely they were to be hyperactive or to have difficulties with hearing, movement, or speech…

In September 2007, Bill Thompson at the CDC published the most comprehensive and definitive study to date. Thompson carefully determined the exact amount of mercury that 1,000 children had received in vaccines and performed more than forty separate neurological and psychological tests. The study, which was published in the New England Journal of Medicine, took four years to complete. Its results were consistent with those of the other six: vaccines containing mercury hadn’t caused harm.

Finally, in January 2008, Robert Schechter and Judy Grether from California’s Department of Public Health took a closer look at the rates of autism from 1995 — six years before thimerosal had been removed from vaccines — to 2007, six years after it had been removed. They found what everybody else had found: the rates of autism continued to increase. In an accompanying editorial titled “Thimerosal Disappears but Autism Remains,” Eric Fombonne wrote, “Parents of autistic children should be reassured that autism in their child did not occur through immunizations.”"

Before Enough Time Had Passed to Assess the Thimerosal – Autism Link in Children, Public Messages Were Confusing

Some studies do show a rise in autism starting when the number of vaccines containing mercury was increased in the early 1990s, as well as a decrease in the past few years now that mercury has been removed from vaccines.

Reading just three books written by “experts,” I feel better for being more informed on the controversy but I still have concerns. I think that we, collectively, still have many unanswered important questions and that better data needs to be collected and assessed. I know that I don’t have the expertise to review and assess the scientific studies so I don’t know if studies are assessing the important, big-picture questions in the most meaningful way… Are there studies that assess the impact of the collective vaccine ingredients on these young vulnerable bodies? Are there studies that consider mercury consumption from other sources? I’m still bothered by the quote from the top of this page about the cumulative doses of mercury from the Hepatitis B:

When mercury can’t get out of the body, it travels to the brain, changes into inorganic mercury, clings to brain tissue, and damages the nervous system. Mercury doesn’t cling to just any part of the brain; it goes exactly to those areas involved in autism: the cerebellum, amygdala, and hippocampus.

What’s even more upsetting is the below, which has led me not to trust anything:

I know that research has not been able to prove that the mercury in vaccines is harmful, and I am relieved that it has been taken out of most vaccines as of 2002. But according to an article in the Los Angeles Times on February 8, 2005, Merck knew in 1991 that the cumulative amount of mercury in vaccines given to infants by six months of age was about eighty-seven times what was thought to be safe… Vaccine manufacturers knew we were overdosing babies with mercury, but no one in the medical community realized the possible implications for almost ten years. Why? Because no one talked about it.

Per The Vaccine Book (page 20), the only vaccines in which mercury is now even an issue are some brands of the flu shot and some tetanus shots. Per page xii, “if you use the right vaccine brands and know in which vaccines mercury is still present, you can get the complete vaccine series 100% mercury free.” So, given the information I have today, I’m minimizing my children’s exposure to mercury when I can, but still vaccinating my children.

Please click on Aluminum to read about another key concern which, based on my limited reading, seems unaddressed.